The following relates to the illumination arts, lighting arts, electrical power arts, and related arts.
Light emitting diode (LED) device-based lamps are employed in diverse outdoor lighting and illumination systems, such as traffic lighting, overhead lighting, billboard lighting, and so forth. In a lamp post suitable for use in such applications, a generally vertical post supports a light head comprising LED devices at an elevated position. Such lamp posts are suitably used in the context of commercial or industrial applications such as commercial signage, parking lot illumination for retail centers, malls, supermarkets, and the like, highway lighting, or so forth.
In commercial and industrial settings, the available electrical power is typically AC power, in a range of 200-480 volts (root mean square or “RMS”) in typical commercial or industrial settings. Residential lighting employs voltages in this range or slightly lower, for example 110 volts in the U.S. and 220 volts in Europe.
LED-based lamps, on the other hand, are typically driven by DC power, and each LED device typically operates at relatively low voltage, e.g. a few volts or less, and relatively high current (of order a few hundred milliamperes to a few amperes current flow per LED device. The light head of a lamp post may include LED devices in series, parallel, series-parallel or other electrical configurations. To match the electrical requirements of the LED devices with the AC electrical power, a power supply is provided, which converts the high voltage AC input power to low voltage DC power suitable for driving the LED-based light head of the lamp post.
The power supply is a frequent point of malfunction or failure. In the case of lamp posts, power supply maintenance is performed by a crew of typically three persons (for example, an electrician, an lift operator, and a third “safety spotter”), at least two of which have some level of specialized training. In another approach, the power supply is located at ground level, and the converted DC power is input to the post-mounted lamp via electrical wires running up the post. This approach has the disadvantage of conducting low voltage, high current d.c. electrical power from ground level to the elevated location of the lamp, which entails high “I2R” resistive power losses. In applications such as highway lighting, parking lot illumination, or so forth, a large number of lamp posts may be employed, making maintenance cost and power consumption substantial concerns.
The following discloses improved approaches that overcome the above-identified problems and others.